In the fields of medicines and the like, granules that are made by drying wet granulated substance produced by extrusion granulators or high-speed stirring granulators, and tablets that are made from the granules are frequently used. To dry the wet granulated substance, fluidized-bed drying devices have been used: granulated substances made by granulators undergo a batch drying process to generate desired granules. However, such a batch-type drying device cannot perform a continuous process. This is why drying devices that continuously dry granulated substances by rotary feeders and the like have been proposed as disclosed in Patent Documents 1 and 2.
As disclosed in Patent Document 3, spray dryers (spray drying devices), too, could be used to produce granules. The spray dryers use a spray unit having a nozzle, rotating disk, or the like to spray slurry, which includes such as raw-material powder, solvents, and binders, and have the slurry instantaneously dried with hot air to generate granules. Meanwhile, in order to dry sludge or any other kind of waste as well as toner particles, loop-type airflow dryers may be used, as disclosed in Patent Documents 4 to 6. The airflow dryers have a vertical loop pipe into which granulated substances are poured along with a large volume of hot air; the granulated substances are circulated in the loop pipe and dried.